As a result of the normal aging process, and as a result of diseases such as AIDS, diabetes, and multiple sclerosis, a patient experiences degeneration in the central portion of the retina of the eye, the macula retinae. This condition causes the patient difficulty in distinguishing anything other than very high contrast objects, such as large black letters on a white background. A normal scene of daily life, such as various foods on a plate, becomes almost impossible to interpret due to the patient's inability to distinguish the light and dark areas of the scene.
The contrast of a scene could be enhanced for the patient by means of a pair of glasses equipped with a video display fed with a video signal from a video camera mounted on the patient's head. The contrast of the video display could be adjusted to enhance the contrast of the scene viewed by the video camera. Unfortunately, such an apparatus would require the patient to carry added weight on his head and get used to a completely new way of viewing the world.
Hence, it is desirable to enhance the contrast of a scene while allowing the patient to view the scene with his own eyes. Such contrast enhancement may be accomplished by selective illumination of the scene. Areas of the scene with high reflectivity are illuminated more strongly, while areas of lower reflectivity are illuminated less strongly. In this manner, bright areas become brighter while dim areas remain dim, resulting in contrast enhancement. To achieve color enhancement, each of the three primary colors may be contrast enhanced independently.
It is also desirable to enhance the edges of features in the scene to distinguish the transition from one feature of a scene to the next.